The present invention relates to electronic circuits in general and, in particular, to power sequencing techniques. As process dimensions for integrated circuits continue to shrink, the maximum operating voltage supplied to the circuits may decrease in a corresponding fashion. Reduction of the maximum operating voltage prevents large electric fields from damaging circuit structures such as gate oxide, diffusion depletion regions, and various insulating layers. However, in many cases, external, system operating voltages have not decreased as rapidly as required by semiconductor technologies with reduced geometries. Therefore, integrated circuits manufactured in advanced semiconductor technologies typically include voltage regulators which are supplied by higher voltages, but output a lower voltage that is compatible with the maximum operating voltage of a particular semiconductor technology.
Additionally, sets of one or more regulators may be included in separate power domains, so that noise coupling from one portion of the circuit to another may be prevented. In addition, there may be functions that are powered in one supply domain and then shared with a circuit that is powered in a separate power domain. For example, a voltage and current reference may supply reference voltages and current to other analog circuits. Another example includes digital control signals that are generated in one power domain but are used to control other digital or analog functions in a separate power domain. Because of these dependencies, novel power sequencing techniques may be desirable to avoid errors and ensure efficient power-on or power-down.